Why do we sleep?
We all know the feeling of not getting enough sleep, but what does sleep actually do for us? lets quickly break down some of the benefits.
Benefits of Sleep
Puts you in a better mood
You probably could have figured that out on your own, but the reason is that with lack of sleep our amygdala (the emotional center of your brain) goes into overdrive while our prefrontal cortex (part of the brain that can calm your emotions down) activity slows down. Essentially our emotions are driving our response to our environment.
Improve focus and maintain executive functioning skills
Our frontal cortex is particularly vulnerable to lack of sleep. This part of our brain is responsible for decision making and judgment. So the phrase “sleep on it” holds true.
Rid the brain of waste
Research is still relatively new in this line of thought, but evidence suggests that toxins are cleared from the brain during sleep. Certain Proteins build up in the brain during the day and are cleared as we sleep. One of these proteins is beta-amyloid that can cause plaque to form in the brain disrupting communication. Build up of these plaques is a telltale sign of Alzheimer’s disease.
Encoding memories
We are exposed to constant stimulus while we are awake and we can’t store all of that information. Sleep is thought to be a way of sorting that information into what is important and transferring that information into long term memories. this process is called memory consolidation and is the reason studying late into the night isn’t always as effective as a good nights sleep.
Repair
Sleep can help to repair your body from injury or muscle soreness. Growth hormone is higher during sleep and can help you build muscle. So if you are spending time at the gym don’t forget that getting adequate sleep is a crucial piece of repair and building of muscle.
Learning new skills
Sleep can actually help you learn! if you are practicing a new motor skill sleep can help you learn this skill. So basically if you are learning how to ski or how to do the next big trick you will be better after a good sleep.
This is incredibly interesting to me and it may be tied to the amount of REM sleep you get. Brain activity during REM sleep is similar to brain activity while your awake, however your body is paralyzed, which may be an adaptation to avoid causing harm to your body while sleeping. It also means the brain is acting out action such as practicing a skill without any danger of injury.
Okay back up, whats REM sleep?
REM sleep stands for Rapid Eye Movement sleep and is the 4th stage of sleep.
Stages of Sleep
Stage one - Light sleep
This stage can be thought of as a transition state when you nod off to sleep. Heart rate, blood pressure, breathing rate and brain activity begin to slow, but not enough to substantially reap the benefits listed above. In this stage of sleep it is very easy for you to be woken up. It usually constitutes about 5% of sleep, but in those who have disrupted sleep this will make up a larger proportion.
Stage two - Sleep
Brain activity will slow much more than in stage one and you will enter a deeper sleep. It will become more difficult to be woken from this stage.
Stage three - Deep Sleep
This is the deepest stage of sleep. Your brain activity slows way down and synchronizes. This stage of sleep is where you see a large part of the cognitive benefits mentioned above.
REM Sleep - Rapid Eye Movement sleep
As you enter REM sleep your brain activity, heart rate and blood pressure all raise to levels similar to those seen when you were awake. Your eyes will also jerk quickly side to side beneath your eyelids, hence the name of the stage. This is where you will experience the most vivid dreams. Your muscles in your body will be paralyzed, which many experts believe is an evolutionary safety mechanism to prevent you from acting out your dreams. This is stage is thought to be where the majority of learning takes place.
Sleep Deprivation
Now that we have an understanding of what is happening while you are sleeping and some of the benefits to getting enough sleep, lets look at some of the problem associated with not getting enough sleep.
Did you know that 1 in 3 adults aren’t getting enough sleep?
Weight gain
Our energy comes from food, so if we don’t get a restful sleep our body starts to crave high sugar and high fat foods. Sleep deprivations leads to high levels of the hunger hormone gherlin and a decrease in leptin the hormone that helps you feel full. This is why on a late night you start to crave snacks.
Cognitive impairment
Lack of sleep effects your judgment and decision making skills. Sleep deprivation will also effect how fast you react to your environment in a similar way to alcohol.
Poor health
Sleep deprivation increases your risk of many serious health conditions.
You are more likely to develop type 2 diabetes
You are more likely to have stiffer arteries, cardiovascular disease and high blood pressure
Increases your risk of developing Alzheimer’s disease
Increased inflammation
Both short and long term sleep deprivation have been shown to increase inflammation throughout the body. Inflammation is thought to be linked to a variety of health conditions from acne to heart disease and arthritis.
Worse appearance
Sleep deprivation leads to less blood flow reducing the plump healthy appearance of skin giving way to lines and wrinkles. Dilated blood vessels near the eye will give the appearance of dark circles under your eyes.
Bad mood
When we are sleep deprived we are more likely to over interpret threats in our environment which means you may see anger on someones face when they aren’t really expressing that. We will also be worse at communicating and less adept to deal with stress.
References
Schreiber, K. and Digiulio, S. (2018). your body on sleep, sleep stages explained. The science of sleep, (1), pp.8-19.
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Borbély AA, Baumann F, Brandeis D, Strauch I, Lehmann D. Sleep deprivation: Effect on sleep stages and EEG power density in man. Electroencephalography and Clinical Neurophysiology. 1981 May 1;51(5):483–93.
Fontvieille AM, Rising R, Spraul M, Larson DE, Ravussin E. Relationship between sleep stages and metabolic rate in humans. American Journal of Physiology-Endocrinology and Metabolism. 1994 Nov 1;267(5):E732–7.
Van Cauter E, Plat L. Physiology of growth hormone secretion during sleep. J Pediatr. 1996 May;128(5 Pt 2):S32-37.